1. Field of the Invention
The present invention relates to an optical disk player for reproducing information recorded in an information recording medium, such as an optical disk or a magnetooptic disk, and, more specifically, to an optical pickup guide mechanism for such an optical disk player.
2. Description of the Related Art
FIGS. 5, 6 and 7 show a conventional optical pickup guide mechanism for guiding an optical pickup employed in a conventional optical disk player. Referring to FIG. 5, the optical pickup guide mechanism comprises a guide unit 4 comprising a fixed guide rail 1 fixed at its opposite ends to the fixed members of the optical disk player, a movable guide rail 2, and springs 3 supporting the movable guide rail 2 for movement in directions indicated by arrows A within a predetermined range. As shown in FIG. 6, an optical pickup 5 is supported between the fixed guide rail 1 and the movable guide rail 2 for movement along the fixed guide rail 1 and the movable guide rail 2 in directions indicated by arrows B radial to the center of an optical disk, not shown. The optical pickup 5 is provided with two wheels 6 in rolling contact with the fixed guide rail 1 and one wheel 6 in rolling contact with the movable guide rail 2. The springs 3 bias the movable guide rail 2 toward the optical pickup 5. The movable guide rail remains parallel to the fixed guide rail 1 when the optical pickup 5 is located with the wheel 6 on the side of the movable guide rail 2 on a line O perpendicular to the movable guide rail 2 at the middle point of the same as shown in FIG. 6. However, when the optical pickup 5 is shifted in either direction, for example, downward as viewed in FIG. 7, and the same wheel 6 is dislocated from the line O, the moment of a force produced by one of the springs 3 differs from the moment of a force produced by the other spring 3 and, consequently, the movable guide 2 is tilted at an angle .theta. to a reference line parallel to the fixed guide rail 1 as shown in FIG. 7.
The wheels 6 are supported on rolling bearings, not shown, for smooth rotation and, in general, each rolling bearing has a radial clearance between the rolling element and the inner ring or the outer ring and the outer ring has an axial play relative to the inner ring thereof. Accordingly, when the movable guide rail 2 is tilted as shown in FIG. 7, the force acting obliquely to the optical pickup 5 dislocates the wheels 6 from their correct axes of rotation to change the position of the optical pickup 5 relative to the fixed guide rail 1. Furthermore, the force applied to the wheels 6 rolling along the fixed guide rail 1 by the tilted movable guide rail 2 varies with the movement of the optical pickup 5 and, consequently, the power required for moving the optical pickup 5 varies with the position of the optical pickup 5, which causes the optical pickup 5 to slip or rattle.
Such adverse effects of the tilted movable guide rail 2, individually or in combination, affects the performance of the optical pickup 5 adversely.